As far as I'm concerned, it's not one action, it's several recent actions. This, the OQueue thing, the automatic bans, getting booted when mass-reporting in the outside world, the "tolerated, for now" blue comment, the massive increase in bots in BGs as well as farming bots going unchecked for far too long. These are exactly the things I noted when I closed my first few accounts prior to the /follow debacle. Basically "you let bots get out of hand and your fixes aren't effective against bots, they just cripple and punnish multiboxers".
While almost none of these directly impact me as a strictly solo PvE multiboxer, it still feels like Blizzard is somehow of the mind that killing multiboxing is the obvious first step. They can easily get rid of us and score an immediate "win" in the eyes of the hissy-fit throwing general population that thinks we're just bot programs that "get away with it" because we're attended. Meanwhile the masses of the real bots that use sophisticated movement are only minimally inconvenienced, if effected at all. The masses are sated if not totally overjoyed by our tears and the belief that getting rid of us fixes everything, and they can feel good about that until the actual bots continue to rise or reappear, at which point Blizzard can go announce a mass ban of reported bots and score another win.
If Blizzard really wanted to throw a monkey wrench in the works of BG Bots, they should have looked more at a means of varying the maps randomly with objects bots can get stuck on and that real players can lead bots into getting trapped on. Rocks, fences, walls, ledges, tree groupings randomly spawned like ore nodes within the map that real players, even multiboxers using follow, can easily react to, but bots that rely on pre-determined pathing or randomly following someone can't seamlessly correct for. While it wouldn't be totally effective and lose effectiveness over time as bots adapt with more varied pathing and "stuck" responses unless Blizz has a ton of obstacle spawn variation, if we were just "collateral damage" as they claim, it would be a better band-aide than the steps they've taken recently, IMHO.